(1) Field of the Invention
This invention relates to a flat electric wire for a wire harness in which a plurality of insulation-sheathed wires are juxtaposed on a plane, a method and an apparatus of producing the flat electric wire and a method and an apparatus of producing a wire harness utilizing the flat electric wire.
(2) Statement of the Prior Art
Electrical devices in an automotive vehicle or common devices are electrically interconnected by wire harnesses. For convenience of explanation, such a kind of a conventional wire harness will be described below by referring to FIGS. 16 to 22. FIG. 16 is a perspective view of a typical wire harness. FIG. 17 is an explanatory view illustrating a position of applying the reinforcing tape for the flat electric wire and an operation of termination treatment. FIGS. 18(a) and 18(b) are explanatory views illustrating the position for applying the reinforcing tape and the operation of termination treatment. FIG. 19 is a perspective view of a conventional flat electric wire. FIG. 20 is a schematic view illustrating a conventional apparatus for producing a wire harness. FIG. 21 is a schematic view illustrating another conventional apparatus for producing a wire harness. FIG. 22 is a schematic view illustrating still another conventional apparatus for producing a wire harness.
A typical wire harness, as shown in, for example, FIG. 16, has a plurality of insulator-sheathed electric wire elements a and connectors attached to opposite ends of the wire elements a. As shown in FIGS. 20 and 21, each wire element a is treated at its end and then inserted into each connector c through a terminal t.
A method shown in FIG. 20 comprises the steps of: drawing the wire element a from a wire supply S; cutting off the wire element a by a given length by means of a measuring device A; stripping an insulator-sheath at opposite ends of the wire element a by means of a striping device B; connecting terminals t to the stripped ends of the wire element a; carrying the wire elements a with terminals on their opposite ends to a connecting device D; and attaching the connectors C to opposite ends of the wire elements a.
Another method shown in FIG. 21 comprises the steps of: preparing a plurality of supplies S having different electric wire elements a; selecting a desired one of the wire elements a from the respective supplies S and cutting off the selected element a by a desired length by means of a measuring device A; clamping the cut-off element a at its opposite ends by grippers g; and treating opposite ends of the cut-off element a by carrying the cut-off element a to a sheath stripper B, a terminal connecting device C and a connector attaching device D.
However, in these methods, the treating work of the wire elements a is troublesome since the wire elements a must be treated at a time. The number of circuits (electric wire elements) between the connectors c increases with progress in electronics. In the case of producing a wire harness with, for example, twenty circuits, a production process requires twenty fold times of a working time per electric wire element. This is very inefficient in terms of production. On the other hand, if the production time and cost for a wire harness (SubAssy) are set to be constant, the working time of a single wire element a will become extremely short. This will not be practical.
Consequently, a so-called flat electric wire P' shown in FIG. 19 has been utilized. Since this wire P' is made of a plurality of single core electric wire elements a juxtaposed integrally, the elements a are not separated from each other and thus the wire is easy to handle. Further, this wire is useful since insulator displacement terminals can be connected to the wire elements at a time.
However, the electric wire P', as shown in FIG. 19, has an integrated insulator sheath for each wire element a and thus is very expensive in comparison with the same number of single core insulator-sheathed electric wire elements a. It is desirable to produce the electric wire P' (wire elements a) as inexpensively as possible since the wire harnesses are used in so many circuits.
FIG. 22 illustrates one of the methods for treating ends of a plurality of electric wire elements a at a time. This method includes the steps of: drawing wire elements a to be connected between connectors c and c from supplies S at the same time; cutting off the wire elements a by a given length by a wire-measuring device A; feeding the cut-off wire elements to termination-treating devices B, C and D; and attaching the connectors to opposite ends of the wire elements a.
In this method, a gripper g draws and feeds the juxtaposed wire elements a. However, the respective wire elements a are sometimes not drawn and fed by the same length since the respective wire elements a are not integrated and the gripper g does not apply an even clamping force to the elements a. Feeding of different lengths of the elements causes an irregular termination treatment of the elements and thus produces inferior goods. Further, when the wire elements a have different diameters, the gripper g must be changed to accord with the different diameters. This necessitates troublesome work.
In addition, since the steps of drawing the wire elements a and treating the ends of the wire elements a are effected on the same line, the producing time (tact) is affected by the slowest treatment time, for example, a treatment of inserting the terminals into the connectors. This will down an efficiency of production.